Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$220.47	9.702%	$241.86	$241.86	$241.85	$241.90
Purchase #2	$108.54	13.257%	$122.9291	$122.93	$122.95	$122.90
Purchase #3	$118.56	4.218%	$123.5609	$123.56	$123.55	$123.60
Purchase #4	$179.67	4.708%	$188.1289	$188.13	$188.15	$188.10
Purchase #5	$37.74	11.286%	$41.9993	$42.00	$42.00	$42.00
Purchase #6	$162.56	4.869%	$170.475	$170.48	$170.50	$170.50
Purchase #7	$245.30	12.714%	$276.4874	$276.49	$276.50	$276.50
7 purchase totals =	$1,072.84		$1,165.4406	$1,165.45	$1,165.50	$1,165.50